The present invention relates to communication equipment for communicating through a telephone line, a structure of a charging terminal for charging a battery stored within a mobile communication apparatus, and an isolating switch used in the communication equipment.
Generally, an internal battery of a mobile communication apparatus such as a portable telephone, a cordless telephone and the like (hereinafter referred to as xe2x80x9cmobile apparatusxe2x80x9d) are charged when the mobile apparatus is placed on a battery charger or a telephone base unit (hereinafter referred to as xe2x80x9cbase unitxe2x80x9d). On the other hand, the base unit has a structure that prevents an electrical shock from the charging terminal of the base unit by maintaining an insulating condition between the charging terminal and a telephone line while the mobile apparatus is not placed in position. An insulating component such as a transformer, a photo-coupler, a relay, a capacitor and the like device is generally utilized as a means to insulate the charging terminal of the base unit from the telephone network. Communication equipment, which is known in the prior art, will be described hereinafter by taking a cordless telephone as an example.
FIG. 15 shows a circuit structure of a base unit of a prior art cordless telephone . In FIG. 15, the base unit 3 is provided with a charging terminal 4 inside of a handset holder (xe2x80x9ccradlexe2x80x9d) so as to charge a battery within a handset 1 by placing the charging terminal 4 on the base unit 3 into contact with a charging terminal 2 of the handset 1, when the handset 1 is stored in the cradle. In FIG. 15, reference numeral 8 represents a power supply, reference numeral 9 represents a transmitting circuit, reference numeral 10 represents a receiving circuit, and reference numeral 11 represents a telephone network. A charging circuit 5 in a secondary stage is separated from an interface circuit 6 in a primary stage with an insulating component 7 such as a transformer, a photo-coupler, a relay, a capacitor and the like, to prevent an electrical shock.
However, the foregoing prior art cordless-telephone is high in cost , because it utilizes the insulating component 7 such as a transformer, a photo-coupler, a relay, a capacitor and the like. Also, degradation in quality of talking sounds can result, if a transformer is used for the insulating component 7, since it causes a transmission loss. Moreover, there has been another problem of obstructing an improvement of sidetone characteristic, in which a transmitting signal makes an entry into a receiver, since it is difficult to match an impedance of the transformer with an impedance of the telephone network 11.
An object of the present invention is to insulate the charging terminal of communication equipment from a telephone network at a low cost, so as to provide communication equipment that is capable of preventing degradation of sound quality and improving the sidetone characteristic. Another object of the present invention is to provide a charging terminal, and an isolating switch for use in the same.
The communication equipment of the present invention comprises a charging circuit, a charging terminal, and an isolating switch provided between the charging circuit and the charging terminal. Further, the communication equipment of the present invention comprises a mobile apparatus equipped with a rechargeable battery, and a stationary apparatus having a charging circuit in it for charging the battery. Both the mobile apparatus and the stationary apparatus have respective charging terminals, and the stationary apparatus includes an isolating switch between the charging terminal and the internal charging circuit. The communication equipment is intended for connection with a telephone network or an electric power line. Furthermore, the isolating switch contains a spring consisting of a first portion having a relatively small spring constant and a second portion having a relatively large spring constant. The foregoing structure of the communication equipment can eliminate an insulating component such as a transformer, a photo-coupler, a relay, a capacitor and the like, so as to achieve a cost reduction of the communication equipment.
A structure of the charging terminal of the present invention comprises a charging terminal disposed on a bottom surface of the mobile apparatus, a charging terminal disposed on the stationary apparatus, and an isolating switch having a lever to be actuated by the mobile apparatus. This structure of the charging terminal of the present invention divides the weight of the mobile apparatus into a direction of force to depress the charging terminal and another direction of force to depress the lever, so as to obtain sufficient contact pressure with the isolating switch with a small amount of force. Distributing the loading direction of the mobile apparatus in this manner can reduce the number of the component parts and simplify the structure.
The isolating switch of the present invention comprises the spring which includes a first portion having a relatively small spring constant and a second portion having a relatively large spring constant, a lever, and a pair of electric contact points. The switch is operated by depressing the lever with a force created by the first portion of the spring, and pressurizing the electric contact points with a force created by the second portion of the spring. The foregoing structure is capable of obtaining proper contact pressure even when a lightweight mobile apparatus is placed on the stationary apparatus, thereby ensuring an electrical connection.